Experiment station bulletins. 495 



(fi) 2 trees alive; o trees dead. 



(7) These trees were all dead last Fall. 



It will be observed that some of these plants stood exposure to a high- 

 er temperature for a longer period than would be necessary to kill San 

 Jose scale. This test is not offered as in any way conclusive, however. 

 It is described here in order to better call attention to the suggestion 

 that possibly a careful and thorough investigation along this and similar 

 lines might be worth while. 



Most household pests succumb readily to heat. For example, adults 

 of one of the common clothes-mothes {Tinea hiselliclla) may be quickly 

 killed at 119° F. A hot flat iron has often been recommended as a 

 means of killing the larvaj of moths in clothing — but might not some 

 practical and safe means of applying heat be arranged to insure valuable 

 clothing in chests or closets against moths? Thus, there are many pos- 

 sibilities for heat, as an insecticide, that have never been carefully and 

 systematically tested as to their larger practicability. 



general conclusions. 



Reductases, catalases and oxidases were found in water extracts and 

 in the insoluble pulp oi' llie tissues of I*. Cornutus and other insects. 

 Moreover, almost certain evidence indicated that the same three kinds of 

 enzyme-like bodies exist in the intact tissues of living insects. 



Heat of certain intensilies, and the several contact insecticides studied 

 (gasoline, carbon-disulphide, hydrocyanic acid gas, sodinm fluoride, 

 etc.), when used at a concentration sufficient to kill insects, deleterious- 

 ly affected the activities of i-eductases, catalases and oxidases — usually 

 in unequal degree, tlnis disturbing the nafui-al or normal balance of 

 such activities. 



If the catalase, oxidase, and reductase activities are actually of as 

 vital importance to llie life processes of the tissue cells as certain 

 evidence indicated, then the deleterious action of the contact insecticides 

 studied in this connection must be an important factor — perhaps, in 

 some cases, the determining factor- — in causing the death of treated 

 insects. 



A study of the influence of the various contact insecticides upon the 

 life processes in nervous tissue cells seems of next importance in this 

 connection. 



Fat or fat-like membrances (e. g., lard and lanoline) absorbed gasoline- 

 vapor (and chloroform-vapor) from air charged Avitli that vapor, and 

 the absorbed vapor rendered the membranes less permeable to oxygen. 

 This finding may, in part, account for the fact that less oxygen was used 

 by an insect deeply under the influence of gasoline, since a similar con- 

 dition existed — in that, under such circumstances, the lipoids of the liv- 

 ing, oxygen-absorbing cells, and of the body fluids surrounding them, 

 were impregnated with gasoline. So also, the same finding may help 

 to explain the fact that, in the presence of air containing gasoline vapor, 

 less hydroquinone was oxidized in an "insect tissue extract plus hj^dro- 

 quinone solution" (in which the reductase had mostly passed) than 

 was the case when the same extract was in pure air. 



Waxen membranes which had been thoroughl^y wet with lime-sulphur 



